The invention relates to a method of determining the combustion air ratio .lambda. (which is the ratio of the quantity of air supplied, to the minimum quantity of air required for the combustion of one unit of quantity of fuel) of a reciprocating-piston internal combustion engine, particularly an Otto engine.
The methods used at this time to determine the combustion air ratio .lambda. in reciprocating-piston internal combustion engines are based on the determination of the air mass, and the fuel mass, or an evaluation of the chemical composition of the exhaust gas. The disadvantage of these methods is that an exact determination of the combustion air ratio cannot be performed for individual operating cycles, particularly at higher engine rpms. In measurement processes employing a so-called leanness sensor, the problem arises of the considerable temperature dependency of this type of sensor, which leads to erroneous measurements without extensive temperature compensation. Moreover, with the aid of a lambda sensor measurement or leanness sensor measurement, ultimately only averaged values can be detected which may still be sufficient for the regulations and/or controls of the fuel supply system of an internal combustion engine. With the aid of a lambda sensor measurement or leanness sensor measurement, however, it is possible to make more precise statements about the operating-cycle-specific combustion air ratio as a function of the combustion process, which is necessary in particular for the optimization of aggregates as a whole, i.e., reciprocating-piston internal combustion engines, including the aggregates needed for regulation and control.